This app allows you to create new calendars in your iCloud account. However, if you want to add a calendar to another service, such as Google Calendar or Microsoft Outlook, you’ll need to do it through their respective websites.
▼How to Add a Calendar to Google Calendar
To add a calendar to Google Calendar, go to the Google Calendar website and follow the steps there. For detailed instructions, check the link below:
(External site) Google Calendar - Create a new calendar
▼Adding a Calendar to Other Services
For other calendar services, follow the instructions provided by each service to add a calendar.